Wallboard, a common construction material, comprises a gypsum core sandwiched between two layers of paper. Manufacturers and vendors of wallboard as well as builders employing wallboard in their construction projects typically generate wallboard scrap as a result of trimming board pieces to fit a particular application. Substantial amounts of scrap are also produced in the demolition of buildings. With ever increasing scarcity of dump space and elevated dumping fees, a significant expense can be incurred in disposing of the scrap material. Moreover, some general purpose dumps do not accept wallboard fragments, requiring disposal in special hazardous waste sites.
Increased disposal costs raise the desirability of recycling the gypsum and paper within the wallboard. Not only would the disposal problem be solved but also selling the recycled components could generate additional income. Prior attempts at recycling wallboard have included processing the gypsum board through a hammer mill to pulverize the gypsum and remove the paper facings. However, such methods are undesirable in that the hammer mill finely pulverizes the paper making separation of the gypsum and paper difficult or impossible. The resulting mixture is unusable. Reducing the speed of operation of the hammer mill as an attempt to resolve this pulverizing problem has not been effective.
Another attempt at recycling wallboard comprised passing the board fragments through a shredder, for example a garden-type shredder or grinder. However, this technique still does not produce a consistent output of material which is well adapted for separation.
Another drawback of prior recycling methods and apparatus relates to the considerable amount of gypsum dust produced during crushing which causes a potential health hazard for workers who breath the dust.